1. Field of the Invention
The present invention relates to a dielectric ceramic composition having a large dielectric constant and a coefficient of thermal expansion nearly comparable with that of alumina, and to a package for packaging semiconductor.
2. Description of the Prior Art
Accompanying the trend toward highly densely integrating the circuits and manufacturing integrated circuits having large capacities in recent years, it has been demanded to produce packages of large sizes for packaging semiconductors or ICs. Furthermore, an increase in the size of the package is accompanied by an increase in the number of connection pins, resulting in an increase in the inductance components due to increased wirings and arousing problems in that noise generates in the output signals of the IC and IC is erroneously operated by undesired reflection. To solve such problems, a ceramic capacitor having a capacitance of about 30 to 100 nF has heretofore been inserted between the power source side and the ground side to absorb noise and to prevent erroneous operation.
In recent years, such a ceramic capacitor has been incorporated in a semiconductor package, and alumina ceramic that is a dielectric has been used as a capacitor of this type. The alumina by itself is an insulator and is a dielectric, too. By utilizing this dielectric, therefore, a capacitor can be incorporated in the package.
However, the alumina has a dielectric constant which is as relatively small as about 9.5 to 10. When a dielectric is formed by alumina, therefore, the area of the dielectric must be increased to obtain a large capacity and besides, the dielectric layers held by the electrode layers must be formed in a plural number, causing the capacitor to become large in size.
A method has been developed to increase the dielectric constant of alumina. However, the dielectric constant is still 18 or smaller. As the ICs having large capacities are being manufactured in recent years, capacitors having large capacitances are demanded resulting, however, in an increase in the size of the capacitor and, hence, in an increase in the size of the package and the substrate because of incorporating such large capacitors and an increase in the cost.
The ceramic capacitor is inserted between the power source side and the ground side. When the capacitor is incorporated in an insulating layer of the package, however, the wiring must be drawn to the ceramic capacitor inevitably accompanied by the build-up of inductance due to the wiring.